Tutorial by Examples: r

__construct() is the most common magic method in PHP, because it is used to set up a class when it is initialized. The opposite of the __construct() method is the __destruct() method. This method is called when there are no more references to an object that you created or when you force its deletion...

When contributors add to a project from different machines or operating systems, it may happen that they use different email addresses or names for this, which will fragment contributor lists and statistics. Running git shortlog -sn to get a list of contributors and the number of commits by them co...

Props are used to transfer data from parent to child component. Props are read only. Child component can only get the props passed from parent using this.props.keyName. Using props one can make his component reusable.

Once setup is completed. Copy the code below to index.android.js or to index.ios.js file to use the props. import React, { Component } from 'react'; import { AppRegistry, Text, View } from 'react-native'; class Greeting extends Component { render() { return ( <Text>Hello {t...

Whenever an object is treated as a string, the __toString() method is called. This method should return a string representation of the class. class User { public $first_name; public $last_name; public $age; public function __toString() { return "{$this->first_...

This example is showing how to query a database with database/sql, taking as example a MySql database. package main import ( "log" "fmt" "database/sql" _ "github.com/go-sql-driver/mysql" ) func main() { dsn := "mysql_usern...

Generally speaking, empty commits (or commits with state that is identical to the parent) is an error. However, when testing build hooks, CI systems, and other systems that trigger off a commit, it's handy to be able to easily create commits without having to edit/touch a dummy file. The --allow-e...

It's a very common extension that allows type classes with multiple type parameters. You can think of MPTC as a relation between types. {-# LANGUAGE MultiParamTypeClasses #-} class Convertable a b where convert :: a -> b instance Convertable Int Float where convert i = fromIntegr...

Normally, string literals in Haskell have a type of String (which is a type alias for [Char]). While this isn't a problem for smaller, educational programs, real-world applications often require more efficient storage such as Text or ByteString. OverloadedStrings simply changes the type of literals...

Standard Haskell allows you to write integer literals in decimal (without any prefix), hexadecimal (preceded by 0x or 0X), and octal (preceded by 0o or 0O). The BinaryLiterals extension adds the option of binary (preceded by 0b or 0B). 0b1111 == 15 -- evaluates to: True

The following expressions are sequenced: a && b a || b a , b a ? b : c for ( a ; b ; c ) { ... } In all cases, the expression a is fully evaluated and all side effects are applied before either b or c are evaluated. In the fourth case, only one of b or c will be evaluated. In the l...

C11 The following expressions are unsequenced: a + b; a - b; a * b; a / b; a % b; a & b; a | b; In the above examples, the expression a may be evaluated before or after the expression b, b may be evaluated before a, or they may even be intermixed if they correspond to several instruct...

Originally proposed by Vincent Driessen, Gitflow is a development workflow using git and several pre-defined branches. This can seen as a special case of the Feature Branch Workflow. The idea of this one is to have separate branches reserved for specific parts in development: master branch is al...

This type of workflow is fundamentally different than the other ones mentioned on this topic. Instead of having one centralized repo that all developers have access to, each developer has his/her own repo that is forked from the main repo. The advantage of this is that developers can post to their o...

With this fundamental workflow model, a master branch contains all active development. Contributors will need to be especially sure they pull the latest changes before continuing development, for this branch will be changing rapidly. Everyone has access to this repo and can commit changes right to t...

Database transactions ensure that a set of data changes will only be made permanent if every statement is successful. Any query or code failure during a transaction can be caught and you then have the option to roll back the attempted changes. PDO provides simple methods for beginning, committing,...

In C++, sequences of characters are represented by specializing the std::basic_string class with a native character type. The two major collections defined by the standard library are std::string and std::wstring: std::string is built with elements of type char std::wstring is built with e...

<!doctype html> <html> <head> <title>Example Page</title> </head> <body> <% 'This is where the ASP code begins 'ASP will generate the HTML that is passed to the browser 'A single quote denotes a comment, so these lines are not exe...

Keyword lists are lists where each item in the list is a tuple of an atom followed by a value. keyword_list = [{:a, 123}, {:b, 456}, {:c, 789}] A shorthand notation for writing keyword lists is as follows: keyword_list = [a: 123, b: 456, c: 789] Keyword lists are useful for creating ordered ...

Strings in Elixir are "binaries". However, in Erlang code, strings are traditionally "char lists", so when calling Erlang functions, you may have to use char lists instead of regular Elixir strings. While regular strings are written using double quotes ", char lists are wr...